TOEFL Listening: ETS-TOEFL听力机经 - 89ZQT387JN82K32EP$

What does the professor imply about tidal turbines? A. They are hard to maintain because they are difficult to see. B. The cost of installing tidal turbines will continue to increase as time goes by. C. Their use is somewhat unrealistic now but will be the benign option in the fliture. D. The technology to create tidal turbines has not yet fully been developed.